Avoid loadshedding in your cold store

NEWS & MEDIA | 09 April 2019

Avoid loadshedding in your cold store

Picture Source: knysnaplettherald.com


The recent and continuing load shedding must be extremely frustrating for cold store owners. Available information suggests that while the situation is not as serious as Venezuela’s, it is likely to continue for the foreseeable future. If union threats materialize to prevent ESKOM’s break up this prognosis could deteriorate.

At the moment the outages are approximately two hours in length. But every time they happen, bigger refrigeration plants may require a manual start up if they are not set up correctly especially if they have variable frequency drives.

 

The VFD drives or the electronic controllers often trip when there is a voltage spike when the power is switched on. Christo van der Merwe of MRE christo@mre.co.za recently said that their service department had gone crazy assisting clients to restart their refrigeration plants but this has normalised as the plant operators are learning to manage the startups. While smaller Freon systems can start themselves, bigger plants need experience to get them going. One customer lost five fan motors in a recent outage.

Here there are two options. Either buy or rent a generator which will power your complete plant, with automatic switching, or go for one which is sufficient to run the operational equipment with automatic switching during working hours only.

 

2014-11-19 001 2014-11-19 057

 

A big commercial cold store, say 8000 frozen pallets plus, could need 1000 KVA. Suitable generators will cost around R2m, although 2x 500 KVAs can be synchronized to run in parallel.  Here there is a saving on capital cost and one setcan be switched off at times of low demand. If a set is down for maintenance you still have the other, and spares are generally easier to come by for the smaller sets.

 

Another cost is diesel usage which, for a 1000 KVA genset on full load, can run at 200 liters per hour. Then space must also be found as close as possible to the main breakers. While a 1000 KVA set can fit in a six meter container sound attenuation requires a twelve meter, excluding the fuel tank. Exhaust pipe arrangements can be considerable and sufficient space must be left around the generator to allow for sufficient air flow.

 

The alternative is a smaller generator set which has sufficient capacity to power equipment necessary to continue operations.

A 125 KVA machine will cost just over R300 000 and use about 25 liters per hour at full power. Sizing a generator requires a survey of the equipment required to operate. LED lighting requires less power than high pressure sodium fittings but possibly more than mobile racks where the motors are heavily geared. Electric chargers for forklifts are big users and should be considered for exclusion. All computer equipment should be isolated by means of a UPS. With a fuel tank in the sub frame and sound attenuated canopies, smaller generators have advantages.

 

AJ550 200319

 

I spoke to Pat Saunders of FG Wilson Generators in Cape Town. They sell AJ Power generators, one of the leading European brands, and have stock on hand.

Although the” high “prices can be off putting, when the actual costs and frustration caused by frequent power outages are calculated at least a smaller generator set can look increasingly attractive. Pat can be contacted on pat@fgwgenerators.co.za.

 

Freezer stores, especially with Storax mobile racking, keep temperature better in power outages than say those with fixed selective racking. The concentration of product is relatively high and there is less cold air to flow out when the door is open. But entrances must be kept closed by means of high speed doors and consideration should be given to air driers to stop moisture from ending up as ice on the cold room floor. If this happens the mobiles will slip and the rails must be cleaned with a wire brush. Barpro does have stock of Ice melt at both its Cape Town and Joburg branches which can be used to melt the ice.

 

Above: Storax mobile racking installed in a cold store
Above: Storax mobile racking installed in a cold store

 

Fruit chill stores normally require more refrigeration than freezers, as the harvested product is loaded into the stores at ambient temperatures and must be chilled rapidly to preserve the quality.

Pat has one seasonal customer in the Hex River valley with 5x 500 KVA sets and looking for more.